Secrecy communication system



Sept. 1926. 1,598,673

0. B. BLACKWELL ET AL SECRECY COMMUNICATION SYSTEM Filed De o. 18, 1920@51 awn M WL Patented Sept. 7, 192 3.

UNITED srATEs PATENT OFFICE.

OTTO B. BLACKWELL, 0F GARDEN CITY, NEW YORK; DE LOSS K. MARTIN, 0]ORANGE, NEW JERSEY; AND GILBERT S. VEBNAM, OF BROOKLYN, NEW YORK,ASSIGNOBS '10 AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A COBIPOBATIONOF NEW YORK.

SECREGY COMMUNICATION SYSTEMS.

Application filed December 18, 1920. Serial 1T0. 431,721.

This invention relates to a signaling system wherein signals aretransmitted by the agency of a high frequency wave modulated inaccordance with said signals, and more particularly to a signalingsystem employing a plurality of high frequency waves. It is the ob ect'of the invention to provide a system of communication wherey secretcommunications between stations may be had to the end that stations,other than those designed to receive, may not receive complete,intelligible signals.

Heretofore in certain types of signaling systems, in which a highfrequency wave is utilized as the agency for transmltting the signals,the signals have been transmitted by electromagnetic waves of a definitehigh frequency or wave length and any station tuned to said wave lengthmight be capable of receiving said signals. invention secrecy isobtained by the transmission of signals on a plurality of wavesofdifi'erent frequencies, successive portions of a message belngtransmitted on waves of different frequencies whereby .a station tunedto one of said waves receives only a partial and thereforeunintelligible disclosure of the communication. The arrangements of thisinvention present the additional secrecy feature that the shifting ofthe low frequency signals or portions of the message, to the varioushigh frequency waves or channels is not accomplished in a cyclic orderbut rather in a random and. variable manner. To this effect printingtelegraph apparatus and key tapes are utilized to shift the lowfrequency signals in a variable manner to the high frequency channels,the shifting being controlled in ac' cordance with the perforations andsetting of the key tape utilized. With this arrangement the messageswould be unintelligible to unauthorized persons, who might have accesstothe medium through or over which the messages are transmitted, unlesssuch persons should be provided with the key tapes utilized at thesending station in addition to other information; Other objects andfeatures of the invention will ap- In the present pear more fully fromthe detailed description hereinafter given,

The arrangements of the invention are illustrated in theaccompanyingdrawing, in the figure of which is shown a sending station of a systemembodying the invention.

In the arrangements of the drawing are shown four low frequency channels1, 2, 3 and 4 from which the low frequency signals, such as fourtelephone messages, may be transmitted through modulating apparatus outover a transmission line L. The modulating apparatus is shownschematically and includes the modulators M M M and'M with which areassociated the high frequency sources A, B, C, and D, which are ofsuitable different frequencies. These modulators may be of the duplexvacuum bulb type illustrated in the U. S. Patent #1343307, dated June15, 1920, in the name of John R. Carson, although other types ofmodulators may be used. These modulating devices are associated with thelow frequency channels 1, 2, 3, and 4, by means of the hybrid coils 1718, 19 and 20, the conductors 5, 6,7 and 8, and over the contacts of aplurality of series of relays, such as the relays 13, 14, 15 and 16, andthe relays 9, 10, 11 and 12. Associated with the above mentioned hybridcoils are the balancing networks N N N and N,. Included in outputcircuits of the modulators are the band filters F F F and F whichreadily transmit the band of high frequencies of the order of theparticular high frequency source associated with each modulator butwhich attenuate and practicall extinguish frequencies outside of saidand. These filters may be of the type illustrated in the U. S. PatentsNo; 1,227 ,113 and No. 1,227,114 to G. A. Campbell. The output circuitsof the modulators are associated with the line L through the hybrid coil21, a

guishes the low frequency currents transmitted over the line L, such asof the normal speech or telegraphic frequencies. In order that themessages coming in over line L may be received over the lines 1, 2, 3and 4, there is associated with the high frequency sources A. B, C andD, the demodulating devices DM DM DM, and DM,,, which may be of theduplex vacuum bulb type illustrated in the U. S. Patent No. 1,343,308,dated June 15, 1920, to J. R. Carson. Included in the input circuits ofthe demodulators are the band filters F,, F F, and F adapted to readilytransmit bands of frequencies respectively such as those from thesources D, C, B and A and to attenuate and extin uish frequenciesoutside of said bands. T e output circuits of the demodulators areassociated with the llnes 1, 2, 3 and 4, by means of the hybrid windings17, 18, 19 and 20, conductors 5, 6, 7 and 8, and over the contacts ofthe series of relavs, such as relays 13, 14, 15 and 16, and relays 9,10, 11, and 12. The operation of the series of relays, such as relays 9,10, 11 and 1:3. and relays 13, 14, 15 and 16, is controlled by theprinting telegraph transmltter 36. the contacts 39 and 40 of which arecontrolled by a perforated key tape, not shown. Associated with the tapetransmitter is the distributor 29 for timing the seucuce of operation ofthe arrangements. The distributor 29 is associated with a, relay 26 andthe pole changing apparatus 25, which in turn is associated with theusual type of composite set 23'assooiated with the line L. Associatedwith composite set 23 is the low pass filter F which readily allows thetransmission of the low frequency currents, such as the telegraphcurrents and the currents from the po e changing apparatus 25, but whichshuts out the ig frequency carrier currents.

Operation of the sending arrangements of the invention is as follows:

The perforated key tape will be inserted in the ta )e transmitter 36 andthe key K thrown. be throwing of key K will close a circuit for therelay 30. This will release the latch and allow the brush of thedistributor to start rotating. When the brush of the distributor crossessegment 31, the following circuit will be closed; from ground, brush ofdistributor, segment 31, conductor 28, winding of relay 26, to batteryand ground. This will operate relay 26 which controls the pole changer25, whereby impulses of either polarity may be transmitted over the lineL to the dist-antstation to'control a distributor thereat, to time thesequence of operation of the receiving arrangements as will be pointedout later. Whenthe brush of the distributor crosses segment 32, acircuit will be closed over conductor 34, magnet- 35, tobattery andground, thereby operating magnet 35. The operation of magnet 35 willallow the contacts 39 and 40 of the transmitter to be pulled down andwill step the erforated ke tape ahead. When the brus passes oil 0 sement 32 the magnet 35 will be released and t to contacts of thetransmitter will-be pressed against the hey tape. If there are no holesin the perforated key tape the contacts 39 and 40 will remain open asshown. Under such conditions none of the relays 9, 10, 11 and 12, or therelays 13, i I

14, 15 and 16, will be operated. Under these conditions, line 1 will beconnected to the modulator M over the back contacts of relays 9 and 13,over conductors 5, and through hybrid coil 17. The line 2 will beconnected to the modulator M over the back contacts of relays 10 and 14,conductors 6 and the h brid coil 18. Line 3 will be connected to themodulator M over the back contacts of relays 11 and 15, conductors 7 andthe hybrid coil 19. Line 4 will be connected to the modulator M over theback contacts of relays 12 and 16., conductors 8 and the hybrid coil 20.It is pointed out that under such conditions the low frequency signalsfrom the lines 1, 2, 3, and 4 will be imressed on diiferent high freuency waves mm the sources A, B, C, an D, and will then be transmittedout over the line L in a well known manner. When the brush of thedistributor crosses segment 33, a circuit will be closed over conductor37 and through the winding of relay 38, to battery and ground, therebyenergizing relay 38. However this will have no eifect at this time asneither of the contacts 39 and 40 were operated and none of the relays9, 10, 11, and 12 and 13, 14 15, and 16 were reviously operated. Whenthe brush of t e distributor again crosses segment 31, the relay 26 andthe pole changing device 25 will operate as previously pointed out totransmit an im also to the distributor at the receiving station. Whenthe brush now crosses segment 32, the magnet 35 will again be operatedand will pull down the contacts and will step the key tape ahead. Forpurposes of illustration let us assume that the perforations in the ta eare now so arranged that contact 39 may e closed and contact 40 mayremain open when the brush now leaves se ment 32.and the magnet 35 isagain release When the brush now crosses segment 33, the relay 38 willbe operated. T is operation of relay 38 and the contact 39 will closethe following circuit from ground and battery, through the windings inseries of the relays 16, 15, 14, 13, and 41, conductor 43, contact 39,conductor 50, armature and contact of relay 38, to ground. The closingof this circuit will operate the relays 16, 15 14, 13, and 41. When thebrush passes off 0 segment 33 the relay 38 will be released. However,the rel 41 will remain locked up as a locking circult will be closedover the contact and armature of relay 41., conductor 51, break contactof ays 13, 14, 15, and 16, and the relay relay 38, to ground. With therela s 13, 14, 15, and 16 o erated, the line 1 wi now be associated withthe modulator M over the back contacts of relay 9 front contacts ofrelay 13, conductor 7 and hybrid coil 19. The line 2 will be associatedwith the modulator M over the back contacts of relay 10 front contactsof relay 14, conductor 8, winding of hybrid coil 20. The line 3 will beassociated with the modulator M over the back contacts of relay 11 andfront contacts of relay l5, conductors 5 and hybrid coil 17. The line 4will be associated with the modulator M over the back contacts of relay12 front contacts of relay 16, conductors 6 and winding of hybrid coil18. When the brush again crosses se ment 31, the pole changing apparatus25 wi 1 again transmit an impulse to the distributor at the receivingstation. When the brush now crosses segment 32, the magnet 35 will againbe operated and present a new set of perforations to the contacts 39 and40. Assume for purposes of illustration that the perforations of the keytape are this time so arranged that contact 40 will be closed andcontact 39 will remain open. Accordingly when the brush now crossessegment 33 and again operates relay 38, the following circuit will beclosed; from ground and battery through the windings in series of therelays 12, 11, 10, 9, and 42, conductor 44, contact 40, conductor 52,armature and contact of relay 38, to ground. This will operate therelays 12, 11, 10, 9, and 42. When the brush passes off of segment 33and releases relay 38, a locking circuit will be closed over the contactand armature of relay 42, conductor 53, break contact of relay 38 toground, and will thereby maintain the relays 42, 9, 10, 11 and 12 in anenergized condition. It is pointed out that with the relays 9, 10, 11and 12 operated, and the relays 13, 14, 15 and 16 unoperated, that theline 1 will be associated w1th the modulator M over the back contacts ofrelay 10, front contacts of relay 14, conductors 6, and winding ofhybrid coil 18. The line 2 will be associated with the modulator M overthe front contacts of relay 11, back contacts of relay 15,.

conductors 7, and winding of hybrid coil 19. The line'3 will beassociated with the modulator M over the front contacts of relay 12,back contacts of relay 16, conductor 8, and hybrid coil 20. The line 4will be associated with the modulator M over the front contacts of relay9, back contacts of relay 13, conductors 5, and hybrid coil 17. It ispointed out that if the erforations in the key tape were such that 0ththe contacts 39 and 40 should be operated, and both sets of'relays suchas the relays 9, 10, 11 and 12, and the relays 13, 14, 15 and 16 shouldbe operated that under such conditions the line 1 would be associatedwith the modulator M over the front contacts of relays 10 and 14,

conductors 8, and hybrid coil 20. Line 2 would be associated with themodulator M over front contacts of relays 11 and 15, conductors 5, andthe hybrid coil 17. The line 3 would be associated with' the modulator Mover the front contacts of relays 12 and 16, conductors 6, and windingof hybrid coil 18. Line 4 would be associated with the modulator M overthe front contacts of relays 9 and 13, conductors 7, and the hybrid coil19.

It will be seen that the low frequency signaling channels 1, 2, 3 and 4may thus be superimposed on the different high frequency channels A, B,C and D, under the control of the key tape. In other words when thereare no perforations in the key tape the channels 1, 2, 3 and 4 will besuperimposed on the channels A, B, C, D respectively. When there is oneperforation in the key tape, such that contact 39 will be closed,channels 1,2, 3 and 4 will be superimposed on channels 0, D A and Brespectively. When the perforations of the key tape are such that theother contact, such as contact 40 is'closed, the channels 1, 2, 3 and 4will be superimposed on the channels B, C, D and A respectively. Whenthe perforations are such that both of the contacts are closed, thechannels 1, 2, 3, and 4 will be superimposed on the channelsD, A, B andC respectively. Accordingly fragments of each of the low frequencymessages may be superimposed at will on different high frequencychannels in a variable and random manner as controlled by theperforations of a key tape, so that anyone who might have access to themedium through or over which messages were being transmitted, and whomight have a receiving instrument tuned to the respective highfrequencies utilized, would only receive fragment-sof such messages, andthese fragments would be so scrambled by the arrangements of thisinvention that they would be utterly unintelligible. While thearrangements of this invention have been shown as operating with fourlow frequencychannels and four high frequency channels, it is pointedout that the arrangements are illustrative only and that by increasingthe number of contacts, such as 39 and 40, the number of perforations ofthe key tape, and the series of relays, such as 9, 10, 11 and 12, and13, 14, 15 and 16, that the invention is capable of operating with moreor less low and high frequency channels as desired.

The receiving arrangements consist of a distributor 29' and, a tapetransmitter 36' substantially similar to the distributor and tapetransmitter used for sending. A relay 77 is provided which controls thelatch whereby the distributor 29' may be started in operation. The relay77 is included in a circuit over the contacts of a polar relay 76, whichwould in turn be connected to the' set 23 as shown. The polar relay 76is controlled by the impulses sent over the lme L from a pole changer,similar to 25, at the distant station which, as has been pointed out, iscontrolled by the distributor thereat. It is pointed out that the relay76 of the receiving system is connected to the upper side of line L. Thepole changer at the distant station which controlsrela 76 would also beconnected to the u per si e of line L. The pole changer is ereinillustrated as connected to the lower side of line L, and it isunderstood that the receiving relay at the distant station would also beconnected to the lower side of line L. With this arrangement there willbe no interference between the pole changer and receiving relay at thesame station. The distributor 29' will be used to control a tapetransmitter 36', the contacts 39 and of which will be wired similar tocontacts 39 and 40 to control the relays, 9, 10, 11 and 12 and 13, 14,15 and 16. Segment 33' of distributor 29' will, in a manner similar tosegment 33 of distributor 29, be utilized to control relay 38. The keytape utilized at the receiving station will be similar to the one usedat the sending station and will be inserted in the transmitter 36' inthe same Iposition with respect to its perforations as t e key ta e atthe sending station. Accordingly w en the perforations in the key tapeat the distant sendin station so control the arrangements that the lowfrequency channels similar to 1 2, 3, and 4 are superimposed on the highfrequency waves A, B, G and D resgectively, as has been pointed out, thedistri utor 29 and transmitter 36 together with the key tape thereatwill control the receiving arrangements so that the low frequencreceiving channels 1, 2, 3 and 4, will be simultaneously connected withthe demodulators associated with the high frequency waves A, B, C and D.When the low frequency channels at the transmitting station are nowshifted to other of the hi h frequency waves a similar shifting willtalie place in the connection of the low frequency receiving channelswith the demodulating arrangements at the receiving station.

It is pointed out furthermore that while the arrangements of theinvention have been specifically shown as associated with a transmissionline, such as L, that the messages might equally well be transmitted bywire-' less apparatus. In such event it would be desirable to substitutefor the pole changing device 25, other apparatus and a separate ra iofrequency for maintaining synchronous operation between the distributorsat the sendin and receiving stations.

While the arrangements have been disclosed in certain s ecificarrangements which have been deemetf desirable it is understood thatthey are capable of embodiment in 8' carrier frequencies, a printin manyand widely varied form: without degartm from the spirit of the inventionas efin in the appended claims.

What is claimed is:

a 1. A transmission system in which a plurality of high frequency.channels are provided as the agency for transmitting low frequency messaes over said system, an equal number 0 low frequency signaling lines,each of said low frequency lines being associated with one of said highfrequency channels, and means for shifting in a random and variablemanner each of said low frequency lines from the high fre uency channelassociated therewith to a hi frequency channel previously associate withanother of said low frequency lines.'

2. A transmission system in which a plurality of high frequency channelsare provided as the. agency for transmitting low frequency messages oversaid system, a plurality of low frequency signaling lines, each of saidlow fre uency lines being associated with one of sai high frequencychannels, a key tape, and means controlled by said key tape for shiftineach of said low frequency linles to other 0 said high frequency channes.

3. A transmission system over which a lurality of low messagefrequencies may e simultaneously transmittedon difi'erent tel'egra htransmitter, and means control ed there y for changing the relationsbetween said low message frequencies and said carrier frequencies overwhich said low message freuencies were previously transmitted so t atsaid low message frequencies will be transmitted over different ones ofsaid carrier frequencies than previously.

4. A sending station, a plurality of modulating devices thereat withwhich are associated different high frequency carrier currents, aplurality of low frequency transmitting clrcuits associated wit saidmodulating devices, a printing telegraph transmitter, and meanscontrolled thereby for changing the relation of said low frequencytransmitting circuits with said modulating devices.

5. A sending station including a plurality of modulating devices withwhich are associated different high frequency carrier currents, aplurality of low frequency transmitting circuits associated with saidmodulating devices, a printing telegraph transmitter, means controlledthereby for changing the relation of said low frequency transmittingcircuits with said modulatin devices, and a receiving station includinga plurality of demodulating devices with which are associated differenthigh frequency currents of the same frequencies as said carrier currentsat said sending station, a plurality of low frequency receivingcireeaera cuits associated with said demodulating de "vices, a printingtelegraph transmitter operating synchronously with the transmitter atsaid sending station, and means controlled thereby for maintaining achange in the relationship between said low frequency receiving circuitsand said demodulating devices similar to the changes 1n relation shipbetween said low frequency transmitting circuits and said modulatingdevices. 10

' In testimony whereof, We have signed our names to this specificationDecember 1, 1920, December 16, 1920, December 1, 1920.

()TTO B. BLACKWELL.

DE LQ SS K. MARTIN.

GILBERT S. VERNAM.

